In recent years, containers such as pouches and paper containers with a spout have been known for containing highly functional foods and for pouring them out through a pouring fitting (hereinafter called spout) shown in FIGS. 14 and 15. To prevent the content from being degenerated with oxygen and to prevent a drop in the flavor retentivity, it is required that not only the container bodies such as pouches and paper containers but also the spouts must permit oxygen to pass through very little. For this purpose, therefore, a composite spout 1 has been proposed according to which a sleeve 10 which is a shielding member having excellent gas barrier property or excellently absorbing oxygen is fitted to the inner wall of the spout.
A sleeve 10 shown in FIG. 10 is fitted being insert-formed in the inside of a spout body 2 of a composite spout 1. The sleeve 10 has a multiplicity of layers, i.e., an inner layer 10b on the inside and an outer layer 10c on the outside with a functional resin layer 10a held between them. These layers are adhered together by interposing an adhesive layer 10d between the functional resin layer 10a and the inner layer 10b, and between the functional resin layer 10a and the outer layer 10c. 
As the functional resin, there can be exemplified a gas-barrier material or an oxygen-absorbing material. The gas-barrier material may be represented by a resin such as an ethylene/vinyl alcohol copolymer. The oxygen-absorbing material may be either the one obtained by adding an oxygen absorber to the gas-barrier resin or the gas-barrier resin itself having a structure for absorbing oxygen. As the oxygen-absorbing material, there can be exemplified a polybutadiene and a polyisoprene which are oxidizing organic materials. As the material of the inner layer 10b and the outer layer 10c, there is used, for example, an olefin type resin which is a thermoplastic resin.
FIG. 17 illustrates a method of forming the composite spout 1 having the sleeve 10 by using an injection-forming apparatus.
Referring to FIG. 17A, the spout is formed by using a male mold 21 and a female mold 31, the male mold 21 having a core 22 of a cylindrical shape maintaining the same diameter from the proximal end thereof up to the distal end thereof, and the sleeve 10 being fitted onto the periphery of the core 22. The female mold 31 is of the split type that opens right and left, and its inner peripheral surface has a shape corresponding to the outer peripheral surface of the spout body shown in FIGS. 14 and 15.
Referring to FIG. 17C, a gate 33 is connected to the right female mold 31b to inject a molten resin from an injection-forming machine that is not shown.
In the above constitution, the core 22 of the male mold 21 is inserted in the female mold 31 to close the metal mold. Then, as shown in FIG. 17C, the molten resin is injected into a cavity 32 from the gate 33. The molten resin forms a portion that becomes the spout body 2 of the composite spout 1; i.e., the composite spout 1 is formed having the sleeve 10 on the inside of the spout body 2 (see JP-A-2001-213455).
When the core 22 has the same diameter in transverse cross section from the proximal end thereof up to the distal end thereof, however, the sleeve 10 is often deviated in the axial direction of the core 22 toward the proximal end side due to the dynamic pressure of the resin injected from the injection-forming machine as shown in FIG. 17D. If the sleeve 10 deviates up to the proximal end of the core 22 as described above, the end surfaces of the sleeve 10 are often exposed in the composite spout 1.
To cope with this problem, there has been proposed a method of producing the composite spout 1 as shown in FIG. 18.
Referring to FIG. 18A, there is no change in the female mold 31 but a stepped portion 29 is formed in the core 22 of the male mold 21 on the side of the proximal end (see a view from an arrow E in FIG. 18) which is nearly equal to the thickness of the sleeve 10 and is at right angles with the axial direction of the core 22, and the one end side of the sleeve 10 is brought into contact with the stepped portion 29. The portion where the stepped portion 29 is formed is brought into agreement with a position where the sleeve 10 is disposed in the composite spout 1.
In this constitution as shown in FIG. 18B, the core 22 of the male mold 21 is advanced toward the female mold 31 to close the male and female molds 21 and 31, and the molten resin is injected from the gate 33 as shown in FIG. 18C to thereby form the composite spout 1. When the molten resin is injected into the cavity 32 in the female mold 31, the stepped portion 29 limits the motion of the sleeve 10 in the axial direction of the core 22 despite the sleeve 10 receives the dynamic pressure of the molten resin.
However, if the motion of the sleeve 10 is limited by forming the stepped portion 29 in the core 22 of the male mold 21 as shown in FIG. 18A, the molten resin does not flow to an end surface 10g on the one end side of the sleeve 10, and the sleeve is fitted in a state of being exposed in an inner space of the composite spout 1 (see a view from an arrow F in FIG. 18). As a result, the end surface 10g of the sleeve 10 is exposed. When the content is filled, therefore, the functional resin elutes out from the functional resin layer 10a constituting the sleeve 10 arousing a problem from the standpoint of sanitation and causing a drop in the flavor of the content or a change of the content.
The present invention was accomplished in view of the above circumstances, and its first object is to provide a composite spout which does not permit a sleeve fitted onto the core to be deviated during the injection forming and does not permit end surfaces of the sleeve to be exposed in the spout body, and an injection-forming apparatus for forming the composite spout.
In forming the composite spout, further, no gap has been formed between the core 22 of the male mold 21 and the inner peripheral surface of the sleeve 10 as shown in FIG. 17A, and the sleeve 10 is exposed on the inner peripheral surface of the composite spout 1. Therefore, there remains a problem in that the sleeve 10 cannot be easily fitted onto the core 22.
Further, the resin does not flow up to both ends of the sleeve 10 of the composite spout 1 that is formed, and the ends of the sleeve 10 may exfoliate. Therefore, the end surface 10g of the sleeve 10 is exposed in the container, the gas-barrier member of the functional resin layer 10a is deteriorated, the oxygen absorber elutes out and, therefore, the functional resin fails to efficiently exhibit its action.
The present invention was accomplished in view of the above circumstances, and its second object is to provide a composite spout which enables a sleeve to be easily fitted onto the core of the male mold and is capable of reliably covering both ends of the sleeve, and an injection-forming apparatus for forming the composite spout.
Further, an end of a discharge port 6 of the composite spout 1 has a small thickness and a small capacity and, therefore, the molten resin is filled therein in only a small amount. Accordingly, the heat of the molten resin is not sufficiently conducted to the sleeve 10 and the sleeve 10 may be poorly melt-adhered to the spout body 2. As shown by a two-dot chain line 10h in FIG. 14 and as shown in FIG. 15, therefore, an end 10e of the sleeve 10 may exfoliate from the spout body 2. With the sleeve 10 being exfoliated, the content in the container may enter into between the spout body 2 and the sleeve 10. As the end surface 10g of the sleeve 10 is exposed in the container, further, the functional resin elutes out from the functional resin layer 10a. When the content is filled, therefore, a problem arouses concerning sanitation, and flavor retentivity of the content drops.
The present invention was accomplished in view of the above circumstances, and its third object is to provide a composite spout which enables a spout body and a sleeve to be reliably adhered together, and an injection-forming apparatus for forming the composite spout.